In known receiving devices the Nyquist slope is realized in the IF frequency range by external, what are referred to as SAW filters, which are also called Surface Acoustic Wave filters. These SAW filters produce channel selectivity and form a Nyquist slope. Due to the multiplicity of television standards worldwide, SAW filters forming different Nyquist slopes are necessary. These SAW filters forming different Nyquist slopes differ in the bandwidth, intermediate frequency and the width of the double-sideband range.
In more recent receiving devices, according to newer concepts for receiving multi-standard television signals, a window-SAW-filter is used instead of a multiplicity of SAW filters. The external SAW filter can also be avoided by an internal selectivity. In both cases, an integration of a Nyquist slope must be realized in order to be able to realize an analog television signal reception.
Typically, a window-SAW-filter is used for receiving digital television signals.